Objective  To investigate the changes of regulatory T cell levels in children with infectious mononucleosis (IM) and its correlation with the concentration of Epstein-Barr virus DNA (EBV-DNA).

  Methods  Forty-two children with IM were selected as observation group, and thirty healthy children as control group. The fasting venous blood samples of two groups were collected, and the expression values of CD3⁺, CD4⁺, CD8⁺, CD4⁺CD25⁺, CD4⁺CD25⁺CD127^- were determined by flow cytometry, and the EBV-DNA concentration was determined by Polymerase Chain Reaction (PCR). The test results of the two groups were compared, and the correlation between the level of regulatory T cells and the concentration of EBV-DNA was analyzed.

  Results  The CD3⁺ and CD8⁺ levels of the observation group were significantly higher than those of the control group, and the CD4⁺, CD4⁺/CD8⁺, CD4⁺CD25⁺, CD4⁺CD25⁺CD127^- levels were significantly lower than those of the control group (P < 0.05). The positive detection rate of EBV-DNA in the observation group was 85.71%, which was significantly higher than 3.33% in the control group (P < 0.05). The EBV-DNA content in the acute phase of the observation group was (76.62±5.10)×10³ copies/mL, and the EBV-DNA content in the recovery phase was (0.68±2.30)×10³ copies/mL. EBV-DNA concentration in the acute phase of IM children was positively correlated with CD3⁺ and CD8⁺ levels, and negatively correlated with CD4⁺, CD4⁺/CD8⁺, CD4⁺CD25⁺, CD4⁺CD25⁺CD127^- levels.

  Conclusion  The level of regulatory T cells in children with IM is negatively correlated with the concentration of EBV-DNA, suggesting that there is a general immune regulatory dysfunction in children with IM in the acute phase, and the degree of immune dysfunction is closely related to the amount of EB virus infection.